Colours without colours
Salts normally appear transparent to white, i.e. they reflect all colours of light that hit them. Without additional colourants, this should not change, should it? Similar to the familiar NV centres, the defect sites in diamonds, there are other colour centres in salts. These are places in the sodium chloride lattice, for example, where there is no longer a chlorine atom but an electron. And it is precisely this electron that absorbs certain colours of light. Due to the absorption of certain wavelengths, the salt appears in different colours, depending on the type. A water colour that is dissolved in water leaves behind a coloured residue as soon as the water evaporates. In contrast, a coloured salt does not. These somewhat dated research findings are increasingly fitting into school lessons thanks to new educational plans. That is why we are currently working intensively on dusting off and, above all, digitising these experiments. On 27.05.25 we were at a school for the last time for the time being and tested our exemplary teaching material on physics and chemistry school leavers. Especially when the lesson includes a flashing and popping Tesla transformer (ā¬30) to generate the colour centres, the pupils forget for a second that it's actually time to hand in their grades.